I am having an same issue.
I added a repeater field with two required sub-fields in it. And the repeater field itself is optional.
It doesn’t happen all the time, but sometimes when I try to update a post (with empty repeater field), suddenly these required sub-fields appear and the message says it cannot be updated because these two required sub fields are empty. And I have to remove these sub fields manually, then I can update the post.
And I am 100% sure I have not entered anything previously for the repeater field.
It’s not just me. Several my co-workers complained it to me.
Here’s screenshot: http://imgur.com/a/zoOCD
– “Links” is a repeater field
– “Link Title” and “Link URL” are requried sub fields of the repeater field.